He didn't have to join, that was his option.
As I said before, this is an all volunteer army. If there had been a draft initiated I could have understood, if not condoned, his running off to Canada but not someone who voluntarily joined not only the US Army but became an infantryman as well.
If he really didn't want to go, if it was totally against his new found concience then he simply should have refused to go. The Army doesn't hogtie and ship people to combat zones. That would cause too much trouble. He probably would have been placed under arrest and court marshalled. He probably then would have spent about 6 months in jail for deriliction of duty and refusal to obey a direct order and then would have been given either a bad conduct discharge or a dishonorable discharge.
Those were his 'correct' options. Desertion is not a very good one if you ask me. He is going to seriously regret his decision, he will be lucky if he gets off with 15 years after his little stunt. He wanted to see his kids grow up, well, he is going to miss a lot.
Stupid decision on his part. Every decision has a consequence, he should have thought of it before 'going over the wall'.